CFD-based optimization of a modified split-type reaction water turbine using response surface methodology

Abstract

This study addresses the need to improve the performance of split-type reaction water turbines (SRWTs) for low-head hydropower applications, where hydraulic losses and flow instability often limit torque output and efficiency. The objective was to optimize a modified SRWT by evaluating the effects of nozzle-edge sharpening angle, guide-pipe length, and guide-pipe diameter on torque and hydraulic efficiency. A CFD-based optimization framework was developed by integrating ANSYS Fluent simulations with Response Surface Methodology using a three-factor, three-level Box–Behnken Design. Fifteen design cases were simulated, and reduced quadratic models were established for torque and hydraulic efficiency, while pressure drop was analyzed as a supporting hydraulic indicator. Results showed that the sharpened nozzle angle had the strongest influence on both responses. The optimum design, consisting of a 52.02 mm guide-pipe length, 112.49 mm guide-pipe diameter, and 64.99° nozzle angle, produced a predicted torque of 31.22 Nꞏm and hydraulic efficiency of 85.31%, which were closely confirmed by CFD. Compared with the baseline design, the optimized turbine improved torque by 41.42% and hydraulic efficiency by 41.44%. These findings demonstrate that CFD coupled with RSM is an effective tool for optimizing SRWT geometry for low-head hydropower applications.